About the cover: Cover shows mouse airway epithelia that were used to study the biology of recombinant adeno-associated virus transduction and how it differs from that of humans. Aquaporin 4 immunostaining (red) of whole-mount mouse polarized airway epithelia grown at an air-liquid interface. Nuclei are stained with DAPI (blue) and scanning electron micrographs of the epithelia were superimposed on the flurescent photomicrograph. For more information, see article by Liu and colleagues, beggining on page 56.